HBASE-1258,1259 ganglia metrics for 'requests' is confusing

git-svn-id: https://svn.apache.org/repos/asf/hadoop/hbase/trunk@753603 13f79535-47bb-0310-9956-ffa450edef68

src/java/org/apache/hadoop/hbase/metrics/MetricsRate.java

@@ -0,0 +1,73 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.hbase.metrics;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+import org.apache.hadoop.metrics.MetricsRecord;
+import org.apache.hadoop.util.StringUtils;
+
+/**
+ * Publishes a rate based on a counter - you increment the counter each
+ * time an event occurs (eg: an RPC call) and this publishes a rate.
+ */
+public class MetricsRate {
+  private static final Log LOG = LogFactory.getLog("org.apache.hadoop.hbase.metrics");
+  
+  private String name;
+  private int value;
+  private float prevRate;
+  private long ts;
+  
+  public MetricsRate(final String name) {
+    this.name = name;
+    this.value = 0;
+    this.prevRate = 0;
+    this.ts = System.currentTimeMillis();
+  }
+  
+  public synchronized void inc(final int incr) {
+    value += incr;
+  }
+  
+  public synchronized void inc() {
+    value++;
+  }
+  
+  private synchronized void intervalHeartBeat() {
+    long now = System.currentTimeMillis();
+    long diff = (now-ts)/1000;
+    if (diff == 0) diff = 1; // sigh this is crap.
+    this.prevRate = value / diff;
+    this.value = 0;
+    this.ts = now;
+  }
+  
+  public synchronized void pushMetric(final MetricsRecord mr) {
+    intervalHeartBeat();
+    try {
+      mr.setMetric(name, getPreviousIntervalValue());
+    } catch (Exception e) {
+      LOG.info("pushMetric failed for " + name + "\n" + 
+          StringUtils.stringifyException(e));
+    }
+  }
+  public synchronized float getPreviousIntervalValue() {
+    return this.prevRate;
+  }
+}